Multipoint switch

ABSTRACT

The invention relates to a multipoint switch for continuously switching different coil branches of a step-down transformer. According to said invention, at least one torque motor associated to various drive configurations carries out different driving functions for individual groups, thereby substituting a conventional motor.

The invention relates to a tap changer for the interruption-free[continuous under load] switchover between different winding taps of acontrol transformer.

Tap changers have been available for decades for voltage regulationensuring high electrical energy supply quality. Their principal modes ofoperation allow them to be subdivided into resistance-type high speedswitches and reactor switches respectively.

The principle of all resistor-type high speed switches [for use in onload tap changers] goes back to the German Patent 474,613 which issuedin 1929 and that describes for the first time the principle of themake-before-break interruption-free switchover between differenttransformer winding taps by means of the insertion of a bridgingresistor. Tap changers based on this principle are known in numerousembodiments. A typical representative is the type “M” tap changer whichis described in the brochure “Tap Changer Type M-Inspection Procedure”of the assignee of the present application. This on-load tap changer hasa tap selector which permits a load free selection of the winding tap towhich the device is to be switched and, in a separate oil filled vesselarranged spacedly thereabove, an on-load switch for the switchinterrupt-free switchover. The actuation of this on-load tap changer iseffected through a motor drive with an electric motor which is set inoperation upon such a switchover on the one hand by the fine selectorand optionally through a preselector to run continuously and on theother hand actuates the on-load switchover through a force accumulator.The motor drive itself lies spatially laterally of and external to thetransformer.

Through rods, chambers, transmission stages and mechanical geneva ormaltese intermittent or escapement drives, the energy is delivered tothe tap changer. When the force accumulator has reached its endposition, that is, is fully retracted, it is liberated from itsarresting device and the spring energy movement or jump operates theload switchover.

In FIG. 1 the operating course or drive train of such a known on loadtap changer has been schematically illustrated. In FIG. 2 a modificationof such an on load tap changer has been shown which instead of the usualpreselector has a multiple coarse selector; this arrangement is alsoknown to the worker in the art.

A further tap changer has been described in the brochure “Load SelectorType V-Inspection Instructions” of the assignee of this application. Inthis type “V” load selector, the preselection of the respectivetransformer winding tap to which the switchover is to be made and thecomponents for the subsequent switchover to it are structurally united.In this case as well, a motor drive is provided with the aforementionedspatial arrangements and which initially pulls in the spring energy orforce accumulator. After the force accumulator has been fully retractedand subsequently triggered, a rotatable switching shaft is actuatedthat, rapidly and without interruption, causes switchover from one fixedcontact to a neighboring to another fixed contact, each electricallyconnected to a transformer winding tap. A typical drive train of such aknown load selector has been illustrated schematically in FIG. 3.

A tap changer of the reactor switching type is for example known fromGerman Patent 4,126,824 as well as from the booklet “Load Tap ChangerType RMV-1 of Reinhausen Manufacturing Inc., Alamo, Tenn., USA.” Theydescribe two load branches which can be preselectable with a tap changerand between which in each of the switchover phases, a switch, here avacuum switching cell, is connected. Each vacuum switching cell can bebridged by a bypass contact which in turn can connect at least one ofthe two load branches with the load output. The actuation of the vacuumswitching cells is effected by respective force accumulators [springenergy accumulators] which can be drawn in by the movement of a driveshaft. For each of the switched phases, between the bypass contact andthe force accumulator a double sided cam is arranged which is rotatedthrough 180° by the drive shaft for each switching step. On the side ofthe double sided cam turned toward the bypass contact there is a groovefor controlling the bypass contact and on the opposite side a furthergroove for controlling the force accumulator which drives the vacuumswitching cell. The control of the force accumulator is thus such thatfor each switching step it is first compressed and then released andthereby can actuate the vacuum switching cell. For actuation of this tapchanger, therefore, a motor drive with an electric motor is providedwhich enables the switchover and on the one hand allows continuousactuation of the selector contacts and on the other, through thedescribed cams, both the bypass contact which can also be continuouslyactuated and also draws in the described force accumulators. When theforce accumulator has reached its end position, that is has been fullydrawn in, its arresting member is released and by spring energy actuatesthe load switch. In FIG. 7 the operating train of this known tap changerhas been schematically illustrated.

A further tap changer of the reactor switching type is already knownfrom German Patent 19 743 864 from which the functional distinctionbetween reactor-principle switching on the one hand and resistance highspeed switching on the other can be seen. In this known tap changer, ina housing for each phase, fixed selector contacts are provided which areswitchable by two movable selector contacts. Further, for each phase,preselector contacts are provided. For each phase, bypass contacts arealso provided and each vacuum switching cell is actuated by means of afastener accumulator. In a separate lateral housing part a singleoperating mechanism is provided for actuating all of the movablecontacts and all of the vacuum switching cells in the correspondingswitching sequence, whereby this single drive operates with an insulatedshaft extending through the housing and acting upon the individualcomponents. A typical operating train of this known tap changer isillustrated in FIG. 8.

With the known tap changers, the drive is effected by an electric motordrive. Such a drive is for example described in WO 98/38661. In such aknown motor drive, all of the mechanical and electrical components whichare required to drive the tap changer are united. The importantmechanical components are the load drive and the control drive. The loaddrive actuates directly the tap changer. It has, for that purpose acorrespondingly dimensioned electric motor. The control drive contains acam disk which with each switch operation of the tap changer rotatesthrough a complete revolution. The cam disks, in addition, have aplurality of switching cams for the mechanical actuation of numerous camswitch or cam-actuated contacts. The control drive also contains meansis for indicating the tap position or the switching step or operation ormode. The electrical components of the motor drive have variouscircuitry assigned thereto. Thus a motor current circuit is provided towhich the terminals of the electric drive motor are connected throughmotor protectors [circuit breakers, fuses], brake protectors and othercircuitry and switching means connected with the current supply lines.Furthermore, a control current circuit and various reporting orindicating current circuits and triggering current circuits for themotor protection switches may be provided.

The control of the motor drive itself is effected in accordance with theprinciples of step switching, that is a device is provided to trigger aswitch step with each single control pulse and enable the switch then toproceed to the end of the specific switching step or operation. Theoutput shaft of the motor drive which is coupled with drive shaft of thetap changer then is able to carry out, after the single control pulsetripping a predetermined exact number of revolutions. In addition, theknown motor drive has, apart from other safety devices a continuousprotective device which prevents, in the event of failure of thedescribed step control, the motor drive from continuing to its endposition.

The described known motor drive has together with the maltese or genevaescapement transmission downstream thereof in the tap changer of theresistance principle high speed switching type, a whole array offunctions to fulfill:

producing a rotational torque with subsequent conversion is into amovement for the tap selector;

transmission of the torque with step up or step down transmission;

drawing in the force accumulator;

conversion of a continuous movement into a stepped movement;

fixing the switching elements after a completed switching step;

position signaling or indication;

mechanical stop or end function.

As a consequence, conventional motor drives for this purpose and theirtransmissions connected to these motor drives have been of complicatedconstruction, have been difficult and expensive to fabricate since theymust be high precision devices and have together with the force storagedevices generally been the most expensive parts of the tap changer.

For a tap changer of the reactor switching type, the described knownmotor drive together with the transmission downstream thereof andespecially the maltese or geneva escapement and the lever reversingtransmission it was required to fulfill the following functions in a tapchanger:

generating a rotational torque with subsequent conversion into amovement for the fine selector as well as, separately therefrom, thepreselector;

actuation of the bypass;

drawing in the force accumulation following actuation of the vacuumswitchover cells;

position indication;

record end or stop function.

Overall the conventional motor drives and their transmissions downstreamfor these applications have also been of complex construction, expensiveto fabricate since high precision is necessary and they also togetherwith the force accumulator usually make up the most expensive part ofthe overall tap changer.

The object of the invention is to provide a drastic simplification ofthe basic structure of tap changes as have been established over thepast decade and have been fixed in the state of the art.

These objects are achieved with a tap changer with the features of theco-equal patent claims 1 or 6 or 11;

The dependent claims relate to respective advantageous possible featuresand modifications of the invention.

The invention presents as the general inventive concept the use of atleast one torque motor known per se as a component of the drive train ordrive stand of a tap changer.

Such torque motors are for example known from the brochures “BrushlessTorque Motors” of the firm Etel. Such a known torque motor functions onthe same functional basis as a linear drive except that the flat lyingstator here is wound into a circle. A torque motor is a servo motoroptimized to a high torque. Modern configurations from an electricalpoint of view include three phase brushless synchronous motors withpermanent excitation. They are used currently in machine toolfabrication. Up to now they have not been utilized or tested in tapchangers or implemented there or found to be utilized basically in tapchanger drives.

It is true that in the East German Patent 58131 from 1967, experimentswere described which were directed to abandoning conventional driveconcepts for tap changers. The solution there, however, was to provide atap changer with as many hydraulically actuated individual drive modulesas there were steps or taps to be switched so that optionally betweenindividual transformer winding taps and not only between neighboringtaps, a switching could be carried out. This hydraulic solution howevernever found realization because of the high functioning risks, forexample the danger of aging in the seals and the hydraulic medium lines.

For switching apparatus generally, various other drive mechanisms havebeen proposed. Thus for example EP 996 135 relates to a magnetictraveling wave drive for a switching device, WO 99/60591 and WO 00/05735describe stepping motor type drives for switching devices. Thesesolutions also have not been found to be usable directly for tapchangers since they do not allow for a spring like movement and overallare problematical for realizing dynamic switch operations particularlyat low temperatures.

Finally, in WO 01/06528 a controlled drive has been proposed for aswitching device which also has not been found to be suitable for a tapchanger.

The provision according to the invention whereby at least one torquemotor is used for the drive of a tap changer has not been suggested bythe developments in drive technology for switching devices generally.

According to the invention, such a torque motor can be a component of atap changer at various points or can be built into the tap changer atvarious locations. It can be arranged outside the transformer housing orchamber and, indeed, above the transformer or laterally of thetransformer. It can however also be arranged within the transformerchamber or housing and can there replace the force accumulator of theload switch, the fine selector drive or also the preselector drive oralso a plurality of those components.

The use according to the invention of one or more torque motors wherebynewly structured positioning devices can be formed, has numerousadvantages. Firstly, neither clutches nor separate transmissions arerequired which significantly reduce the number of parts. Furthermore, itenables a compact construction to be realized. Because of reducedelasticity or play, there is a high degree of stiffness and because ofthe reduced mass and minimal inertia, a higher dynamic with thepossibility of achieving spring like or jump or step function responsesto thereby make the conventional force accumulator superfluous.

Finally using a suitable control each respective switching step can beimpressed independently from specially effective coutermovements sothat, for example, temperature influences can be largely excluded. Theinvention will be described in greater detail in the following basedupon the schematic illustrations which show:

FIGS. 1 through 3 previously described drive trains or sequences ofknown tap changers of the resistance rapid acting type in schematicillustration.

FIGS. 4 a, 4 b and 5 a and 5 b schematic possibilities of theapplication of the invention of at least one torque motor in anunder-load tap changer of this type.

FIGS. 6 a, 6 b schematic possibilities of the application in accordancewith the invention of at least one torque motor in a load selector ofthis type.

FIGS. 7 and 8 previously described drive trains or drive sequences ofknown tap changers of the reactor type in schematic illustrations.

FIGS. 9 a, 9 b, 10 a, 10 b, 11 a and 11 b schematic possibilities of theapplication according to the invention of at least one torque motor in afirst tap changer of this type.

FIGS. 12 a, 12 b schematic possibilities of the application according tothe invention of at least one torque motor in a second tap changer ofthis type.

In the following schematic illustrations, the components according tothe invention, each of which contains a torque motor, are respectivelydesignated as “positioning unit” and indicated in a gray background. Ineach field the concrete function has been written in which is carriedout by the respective torque motor, that is the respective positioningunit.

In FIG. 4 a the configuration of a tap changer located externally of thetransformer has been shown and here, according to the intention has atorque motor which has replaced the previous motor drive and thetransmission downstream thereof and directly acts upon the forceaccumulator of the load switch, the maltese or geneva escapement ordrive of the fine selector and optionally upon the preselector or courseselector. Beneath it a further embodiment of the intention has beenschematically illustrated in which a torque motor also replaces theprevious force accumulator in accordance with the state of the art andthe associated transmission in which this new positioning unit with thetorque motor acts directly upon the maltese or geneva drive of the fineselector and optionally on the preselector as well as directly on theload switch. The second embodiment can as a whole also be located withinthe transformer as shown in FIG. 4 a.

In FIGS. 5 a and 5 b, further embodiments of the invention have beenschematically illustrated.

In FIG. 5 a, a construction of the tap changer externally of thetransformer has been shown in which a first torque motor, according tothe invention directly actuates the load switch in that it also makessuperfluous the previous force accumulation (left hand positioningunit); a further torque motor (right hand positioning unit) actuatesdirectly the maltese or geneva drive of the fine selector and optionallythe preselector. In contrast to the embodiment of the invention in FIGS.4 a and 4 b in which receptively only a single torque motor has beenprovided, here a plurality of such positioning units with torque motorsare shown.

There below, is than a further modified embodiment of the inventionwhich has a total of three such torque motors. A first positioning unitaccording to the invention (left) actuates directly-eliminating theprevious force accumulator the load switch, a second positioning unit(center) actuates directly the fine selector, and a third positioningunit (right) directly actuates the preselector if one is provided. InFIG. 5 b, these embodiments of the invention are shown in aconfiguration of the tap changer located within the transformer.

In FIGS. 6 a and 6 b with the same type of scholastic illustration,possible embodiments of the invention of the tap changer of the loadselection type have been shown.

FIG. 6 a again shows the arrangement of the tap changer externally ofthe transformer. FIG. 6 b shows the arrangement within the transformer.

The upper illustration in each discloses an embodiment in which a torquemotor directly actuates the force accumulator which in a conventionalmanner drives the switching column with a spring action and additionalcan optionally operate the preselector. The middle illustrations showsreceptively embodiments of the invention in which the torque motor alsoassumes the function of the prior force accumulator and directly derivesthe switching column with the spring like jump or impulsive rotation.The lower illustration finally shows in each case an embodiment with twoseparate torque motors such that the first of these new positioningunits directly rotate the switching column with the spring likeimpulsive action and the second positioning unit separately actuates apreselector if one is provided.

In FIG. 9 a, the arrangement of the tap changer externally of thetransformer has been shown in the upper half of the illustration there,according to the invention, a torque motor replaces the entire motordrive and acts directly on the drive shaft and the reroutingtransmission. The drive shaft in turn actuates in each phase thepreselector, fine selector, bypass contact as well as through the forceaccumulator (not shown), the vacuum switching cell. There below afurther embodiment of the invention has been schematically illustratedwhich a torque motor in each phase forms respectively a new positioningunit and the positioning units act upon the previous remountingtransmission or drive.

FIG. 9 b shows a corresponding arrangement for a tap changer locatedwithin the transformer.

In FIGS. 10 a and 10 b further embodiments of the invention have beenschematically illustrated.

In the upper part of FIG. 10 a, in each phase a first torque motor isshown whose transmission simultaneously actuates the preselector a fineselector while a respective second torque motor actuates the bypasscontact as well as the vacuum switching cell through a force accumulatorwhich can be loaded by that second torque motor. There below a furtherembodiment of the invention is illustrated in which in each phase atotal of three such torque motors are provided which together with thecorresponding transmissions form an independent positioning unit and actdirectly upon the preselector or fine selector or the bypass switch aswell as upon the force accumulator of the vacuum switching cell.

FIG. 10 b shows these embodiments again for an arrangement of the tapchanger within the transformer.

In FIGS. 11 a and 11 b further modified embodiments of the invention areillustrated. In these embodiments the need for certain individualcomponents of previously used systems can be eliminated. A first torquemotor here actuates the preselectors of all three phases, a secondtorque motor the fine selector of all three phases and a third torquemotor both the bypass contacts as well as the force actuators andtherewith the vacuum switching cells of all three phases.

In FIGS. 12 a and 12 b in the same type of schematic illustration,possible embodiments of the invention of a tap changer of anotherconventional type have been shown and whose known drive train accordingto the state of the art has been illustrated in FIG. 8 and alreadydescribed. The upper illustrations show respectively embodiments inwhich a single torque motor actuates through respective interveningtransmissions, the preselector, the fine selector and simultaneously thebypass contact and vacuum switching cell, again through a forceactuator. The middle illustration There below shows respectively in eachphase two such torque motors. A preselected and fine selector isactuated by one of them and the other actuates the bypass contact andthe force accumulator for the vacuum switching cell.

Finally at the bottom further variants have been shown in which in eachphase three torque motors are provided for actuation:

one for the preselector, one for the fine selector and one for thebypass and the force accumulator of the vacuum cell. Here as well it ispossible to provide a phase-wise arrangement and for all of theillustrated arrangements in FIGS. 12 a and 12 b the actuation of theindividual described components simultaneously for all three phases byrespective positioning units. The described FIG. 12 a applies to thearrangement of the tap changer outside the transformer and FIG. 12 b toits arrangement within the transformer.

1. A tap changer for the interruption-free switching between different winding taps of tapped transformer in accordance and the principle of a resistance-type rapid acting switch, comprised of a fine selector and optionally of a preselector for the powerless selection of the winding tap to which a subsequent switchover is to be effected, comprised in addition of a load switch for the subsequent rapid switchover from the previous winding tap to the selected winding tap with a brief insertion of at least one bridging resistance, whereby both the fine selector and the optional preselector and also the load switch is actuatable by a drive, characterized in that a torque motor is provided as the drive.
 2. The tap changer according to claim 1 characterized in that at least one torque motor as well as a known force accumulator actuates the load switch as well as the fine selector and optional preselector.
 3. The tap changer according to claim 1 characterized in that at least the one torque motor actuates directly both the load switch and the fine selector and optional preselector.
 4. The tap changer according to claim 1 characterized in that at least one first torque motor respectively directly actuates the known force accumulator of the load switch and at least one second torque motor respectively actuates the fine selector and optional preselector.
 5. The tap changer according to claim 1 characterized in that at least one first torque motor respectively actuates the load switch directly, at least one second torque motor respectively actuates the fine selector and optionally a third torque motor respectively actuates the preselector.
 6. A tap changer for uninterrupted switching between different winding taps of a tapped transformer in accordance with eh principle of a resistance type rapid switch, comprised of a load selector for the simultaneous selection of the winding tap to which switchover is to be effected, as well as for the rapid switchover for the previous to the selected winding tap with brief insertion of bridging resistance, whereby for the switchover a spring like jump switching element, especially a switching column is provided, characterized in that as a drive for that switching element a torque motor is provided.
 7. The tap changer according to claim 6 characterized in that the at least one torque motor directly actuates a known force accumulator which in turn displaces the switch element with a spring like jump in known manner and also actuates any optional preselector.
 8. The tap changer according to claim 6 characterized in that the at least one torque motor directly displaces the switch element with the spring like jump and also operates any optional preselector.
 9. The tap changer according to claim 6 characterized has in that an at least one first torque motor directly displaces the switch element with the spring like jump and optionally at least one second torque motor directly actuates the preselector.
 10. The tap changer according to claim 1 characterized in that the load switch on the one hand and the fine selector and optional preselector on the other are arranged to be specially separate from one another and/or the fine selector and optional preselector are separately drivable by at least one stepping motor.
 11. The tap changer for uninterrupted switching between different winding taps of a tap transformer in accordance with the principle of a reactor switching, comprised of a fine selector with two load branches between which in each of the switching phases a vacuum switching cell is arranged, comprised of a preselector, comprised of a bypass contact which bridges the vacuum switching cells respectively and in turn connects at least one of the two load branches with the load output line as well as a force accumulators which actuates the respective vacuum switching cell; whereby a single drive is provided which by means of various transmissions and drive shafts actuates all of the mentioned parts, characterized in that as the drive at least one torque motor.
 12. The tap changer according to claim 11 characterized in that the at least one torque motor actuates all drive shafts.
 13. The tap changer according to claim 11 characterized in that separate three separate torque motors are so arranged that each of them actuates the parts of one phase, namely, the preselector, fine selector, bypass contact and force accumulator of the vacuum switching cell.
 14. The tap changer according to claim 11 characterized in that for each phase other separate torque motors are provided, one of which actuates a preselector and fine selector and the other actuates the bypass contact and force accumulator of the vacuum switching cell.
 15. The tap changer according to claim 11 characterized in that for each phase three separate torque motors are provided of which respectively actuates the preselector, one actuates the fine selector and one actuates both the bypass contact and also of the force accumulator of the vacuum switching cell.
 16. The tap changer according to claim 11 characterized in that a total of three separate torque motors are provided of which one actuates the preselectors of all three phases, one other actuates the fine selectors of all three phases and the third both the bypass contacts and also the force actuator of the vacuum switching cells. 